Because there are problems with using a rimfire cartridge, (reliabilty of feeding) and the .22 mag does not have the range or power of a centerfire cartridge.
The SOAR (Special Operations Assault Rifle).
The first true assault rifle debuted in 1942.
German Stg 44, IIRC
The AK-47 assault rifle was made in the Soviet Union. It was designed by Kalashnikov. It has features taken from a variety of different rifles. He was lying in a hospital bed during World War 2. His rifle had jammed. He dreamed of a rifle that could get muddy and would still fire. He created such a rifle.
The AK74 assault rifle is made in the Izhmash weapons plant in Izhevsk, Russia.
No. The function of it is what makes it an assault rifle. An assault rifle fires an intermediate cartridge and has a select fire option (either auto or burst). In the political sense, the determination of what made a so-called "civilian assault weapon" was determined by the BATF (now BATFE) based on the presence of two or more cosmetic features (such as bayonet lugs, pistol grips, and flash suppressors).
The M16 assault rifle's bolt and bolt carrier are made of steel.
The .308 was too powerful for an assult rifle, but the US Army gave it their best try in the 1960's, equipping the M14 rifle with numerous modifications to make it into an assault rifle. As a squad auto weapon it was probably quite adequate, but the .308 was just too powerful a round for use in weapons defined as assault rifles. If other armies tried to develop an assult rifle using the .308 cartridge, nothing ever came of it to the best knowledge of this contributor.
The Steyr AUG (Armee Universal Gewehr) assault rifle was designed in 1977 and entered production in 1978.
You will have to check with the company that made it.
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There is no such thing as a "semi-automatic assault rifle" except in the minds of those politicians and wealthy people who think they should dicatate what you or I can own. The semi-automatic SKS made by Norinco is worht 75-300 USD